1. Field of the Invention
This invention relates to a developing apparatus using a powder developer, and particularly to a developing apparatus applicable to the developing means of an image forming apparatus such as a printer, a facsimile apparatus or a copier utilizing the electrophotographic method or the electrostatic recording method to effect image formation.
2. Related Background Art
In an image forming apparatus utilizing the electrophotographic method, an electrostatic latent image is formed on a photosensitive body as an image bearing member, and the electrostatic latent image is developed by a toner to thereby form a toner image, which is then transferred onto a transferring material to thereby obtain an image.
As the above-described developing method, generally a monocomponent developing method using a monocomponent developer comprising only a toner that is simple in construction of a developing apparatus and is easy to maintain, as compared with a two-component developing method using a developer comprising magnetic particles and a toner and therefore, many developing apparatuses based on the monocomponent developing method have been proposed. Also, a developing method by a nonmagnetic monocomponent developing method not using a magnetic toner has been proposed, and this developing method is put into practical use to cope with the recent requirement for color images.
FIG. 7 of the accompanying drawings is a schematic cross-sectional view showing an example of the conventional developing apparatus using the nonmagnetic monocomponent developing method.
In this figure, the reference numeral 120 designates a rotatable developing roller as a developer carrying member, and it substantially abuts against a photosensitive drum 130 as an image bearing member in a developing portion. A toner supplying and collecting roller 121 as a developer supplying and collecting member and a regulating blade 122 as a developer regulating member abut against this developing roller 120.
The regulating blade 122 is comprised of a support member 122a formed of phosphor bronze or the like and an elastic member 122b of urethane rubber or the like adhesively secured to the fore end thereof, whereby it has the action of forming a thin layer of toner on the surface of the developing roller 120 and imparting charges to the toner.
The toner supplying and collecting roller 121 comprises a mandrel 121a of SUS or the like and an elastic member 121b of urethane foam or the like covering the outer peripheral surface thereof, whereby it has the action of supplying the toner (not shown) stored in a developing container 123 to the surface of the developing roller 120, and scraping off the toner returned without contributing to the developing step from the surface of the developing roller 120. The reference numeral 124 denotes a toner agitating member for agitating the toner.
By such a construction, a thin layer of nonmagnetic toner is formed on the developing roller 120, and an electrostatic latent image on the photosensitive drum 130 can be developed to thereby obtain a toner image.
Now, in the above-described conventional non-magnetic monocomponent developing method, the toner supplying and collecting roller 121 abuts against the developing roller 120 and rotates and frictionally slides to thereby effect the supply and collection of the toner. Also, the imparting of charges to the toner is effected chiefly by the contact friction when the toner passes the regulating blade 122.
That is, during the time until the toner in the developing container 123 is developed on the photosensitive drum 130, a mechanical load (stress) applied to the toner is very great, and the damage of the toner is very great as compared with that in the other developing methods.
Also, in this non-magnetic monocomponent developing method, not only is the load applied to the toner great, but also a load applied to a developing device itself is great. Furthermore, in the case of the above-described toner supplying and collecting roller 121 using a sponge roller if frictional sliding relative to the developing roller 120 continues for a long time, there is wear and damage of the toner supplying and collecting roller 121. In addition, clogging or the like of the toner occur. Consequently, the performance of the toner supplying and collecting roller 121 becomes insufficient, and good toner supply may become impossible.
Further, when a great deal of image formation has been effected, the toner which has not contributed to development cannot be collected by the toner supplying and collecting roller 121 and is accumulated little by little on the developing roller 120, and in some cases, such toner might be fused on the developing roller 120 and the regulating blade 122 to thereby cause bad image formation.
It is an object of the present invention to provide a developing apparatus which can stably form good images.
It is also an object of the present invention to provide a developing apparatus which enables any toner residual on a developing roller to be effectively collected and can effect good image formation.
It is also an object of the present invention to provide a developing apparatus comprising:
a developing carrying member carrying a developer thereon, the developer carrying member carrying the developer carried thereon to a developing portion, and developing a latent image formed on an image bearing member by the developer in the developing portion;
developer supplying means for supplying the developer to the developer carrying member, the developer supplying means being provided in non-contact with the developer carrying member; and
developer collecting means for collecting any developer residual on the developer carrying member after having passed the developing portion;
wherein during a period when the developing operation is not being performed, the developer on the developer carrying member is collected by the developer collecting means with the supply of the developer by the developer supplying means being stopped.
Other objects and features of the present invention will become more fully apparent from the following detailed description when read with reference to the accompanying drawings.